Having fixed the \(\mathcal {B_{QCD}}\)  and \(\xi \)  parameters, we go back
to (REF ) and (REF ) and, obtaining \(\epsilon \)  and \(p\) 
for successive values of \(\rho _B\) ,
we construct the EOS in the form \(p = p(\epsilon )\) , plotted in Fig. 2a.
In the figure, the different lines correspond to the three parameter sets
listed in Table I.
In this type of plot the slope is the speed of sound,
which, due to causality, can not exceed the unity. This limit is shown by the
full lines in the figure. In Fig. 2b we show the corresponding values of the
speed of sound. As it can be seen, our model yields a much stiffer EOS, with
a speed of sound much larger than the conformal value, for which
\(c^2_s = 1/3\) .
The dot-dashed line shows the EOS obtained from a recently
updated version of the MIT bag model [1]}, [2]}, which reads
\(p(\epsilon ) = \frac{(\epsilon - B_{eff})}{3} -\frac{a_2^2}{12 \pi ^2 a_4}\left[1 + \sqrt{1 + \frac{16 \pi ^2 a_4}{a_2^2} (\epsilon - B_{eff})} \right],\) 
